Blinding in Rehabilitation Research: Empirical Evidence on the Association between Blinding and Treatment Effect Estimates

Objective The aim of the study was to assess the association between different types of blinding on treatment effects estimates in the area of rehabilitation. Methods Evidence synthesis was used for the design of the study. This study included any systematic review or meta-epidemiological study that investigated associations between any blinding component and treatment effects estimates in randomized control trials in the area of rehabilitation. The information obtained from the included studies was organized by type of blinding and summarized using a narrative and/or quantitative approach when possible. If there were enough data of estimates for any type of blinding, we decided to pool them in an exploratory fashion. Results The literature search identified a total of 1015 citations, of which 7 studies fulfilled the inclusion criteria. Studies show overestimation, underestimation, or neutral associations for different types of blinding on treatment effects. Conclusions Associations were mixed and did not follow a consistent pattern. Lack/poor reporting of blinding, small sample sizes, and heterogeneity of data sets could have led to nonsignificant and inconsistent results obtained by the included studies. Although the evidence regarding the association between blinding and treatment effect estimates is still inconclusive in the rehabilitation field, based on the available literature, researchers should select creative solutions to avoid performance and detection bias.